Process for making non-staining colored particles for improving aesthetics of a liquid automatic dishwashing detergent product, the particles, and a composition

ABSTRACT

A process for forming a non-staining colored composite particle suitable for incorporation in a bleach-containing or a non-bleach-containing liquid detergent composition is disclosed. The process includes the steps of forming a colored liquid dispersion of pigment particles in a first liquid medium wherein the size of the pigment particles in the colored liquid dispersion is no greater than about 5 mum. The process includes the step of mixing the colored liquid dispersion with a polymeric material and a second liquid medium to form a sprayable colored polymeric material. The process also includes the step of spraying the colored polymeric material on a composite particle and forming a colored polymeric coating on the composite particle. A non-staining colored particle and a liquid ADW detergent composition are also disclosed.

This application claims benefit of application No. 60/130,044 filed Apr.19, 1999.

TECHNICAL FIELD

The present invention generally relates to liquid automatic dishwashingdetergent compositions. More particularly, the invention relates to aprocess for making colored particles that can be incorporated into ableach-containing or non-bleach-containing liquid automatic dishwashingdetergent composition for improving the aesthetics of the liquidcomposition wherein the colored particles do not stain the plasticsurfaces of dishware or an automatic dishwasher.

BACKGROUND OF THE INVENTION

Consumers of liquid ADW products have a preference for such productshaving a certain color or appearance. The addition of solid particlessuspended into a liquid ADW composition can improve the aesthetics ofthe product by simply improving the physical appearance of the product.This is particularly true if the particles are colored and their coloris matched effectively to the base color of the liquid ADW composition.

Previously used particles in liquid ADW products have had a majordisadvantage of contributing negatively to unwanted filming,particularly on glass, stainless steel and plastic surfaces. This isbecause the previously used particles have been coated withwater-insoluble coatings, such as waxes, which melt and are releasedinto the wash solution due to the high temperature encountered duringthe automatic dishwashing process.

Further, in the arena of bleach containing liquid ADWs, the particlescannot be colored by simply using a dye, because during storage of theliquid ADW product, the dye gets bleached. Thus, the formulators have touse bleach-safe pigments to impart an aesthetically pleasing color.Before this invention, the incorporation of pigments posed a majorproblem: the color of the pigment is found to detrimentally stainplastic surfaces, such as plastic dishware and the internal plasticsurfaces of a dishwasher.

It has been desirable to have a process by which colored pigment basedparticles can be made for incorporation in bleach-containing ornon-bleach-containing liquid ADW product, such that the particles arenon-staining. It has also been desirable that the solid particles do notdissolve in the liquid ADW product, but dissolve rapidly in the washsolution during automatic dishwashing. It has been desirable to have aliquid ADW product having solid particles that do not cause asignificant amount of unwanted filming on glass, stainless steel andplastic.

The inventors of the present invention have discovered a process ofcoating the particles with a pigment in a manner such that the particlesare non-staining. This invention is not limited to justbleach-containing liquid ADWs and is also applicable tonon-bleach-containing liquid ADWs that are incorporated with prills orparticles colored with pigments. The present invention is thus directedto overcome one or more of the problems as set forth before.

SUMMARY OF THE INVENTION

The invention meets the needs above by providing a process for forming anon-staining colored composite particle suitable for incorporation in ableach-containing or non-bleach-containing liquid detergent composition,a non-staining colored composite particle and a liquid dishwashingdetergent composition.

In one aspect of the present invention, the process includes the stepsof forming a colored liquid dispersion of pigment particles in a firstliquid medium. The size of the pigment particles in the colored liquiddispersion is no greater than about 5 μm. The process includes the stepof mixing the colored liquid dispersion with a polymeric material and asecond liquid medium to form a sprayable colored polymeric material. Thepolymeric material being selected from the group consisting of alkylcellulose ethers and polyvinyl alcohol. The process also includes thestep of spraying the colored polymeric material on a composite particleand forming a colored polymeric coating on the composite particle.

In another aspect of the present invention, a non-staining coloredcomposite particle suitable for incorporation in a bleach-containingliquid detergent composition is disclosed. The particle is made by theprocess as set forth above.

In yet another aspect of the present invention, a liquid automaticdishwashing detergent product is disclosed. The product includes aliquid dishwashing detergent composition containing chlorine bleach, andnon-staining colored composite particles. The particles are made by theprocess as set forth above.

DETAILED DESCRIPTION OF THE INVENTION

In the preferred embodiment of the present invention, the processincludes the steps of forming a colored liquid dispersion of pigmentparticles in a first liquid medium.

Pigment Processing

The size of the pigment particles in the colored liquid dispersion isdesirably no greater than about 5 μm. preferably no greater than about 1μm, more preferably no greater than about 0.1 μm, and most preferably nogreater than about 0.01 μm. It has been surprisingly discovered thatwhen the pigment particle size in the pigment-liquid dispersion ismaintained within the above size limitations, the resultant pigment,when deposited on a particle as a part of the sprayable polymericslurry, is essentially non-staining. i.e., its color does not transferonto plastic surfaces. The selection of the pigment particle size is thekey to the present invention. One skilled in the art can apply othermeans for achieving a pigment particle size in the size limitation asdisclosed above.

In the preferred embodiment, the first liquid medium is preferablywater. Optionally, a minor amount of a nonionic surfactant is added tothe water to improve the dispersion of the pigment. Typically, thissurfactant is added in an amount no greater than about 10% by weight.

In the preferred embodiment, the process includes the step ofmaintaining the amount of surfactants used in the bleach-containingliquid detergent composition at a preselected value such that when thebleach-containing liquid detergent composition is diluted in a washsolution, the amount of surfactant delivered in the wash solution isless than critical micelle concentration. The term “critical micelleconcentration” is well known to those skilled in the art and need not beexplained any further for purposes of brevity.

Polymeric Coating

In the preferred embodiment, the colored polymeric coating is insolublein the liquid automatic dishwashing detergent composition but soluble inautomatic dishwashing wash solution. The coating is prepared frommaterials which are insoluble in the liquid automatic dishwashingdetergent composition but soluble in automatic dishwashing washsolution. The coating is prepared from materials selected from the groupconsisting of alkyl cellulose ethers and polyvinyl alcohol.Alternatively, the coating is prepared from alginate. Desirably, thealkyl cellulose ethers are selected from one of methyl cellulose andhydroxypropyl methyl cellulose (HPMC). Preferably, the coating isprepared from methyl cellulose having a number average molecular weightdesirably in a range of from about 5000 to about 100,000, morepreferably from about 10,000 to about 20,000, and most preferably, about14,000. The preferred methyl cellulose is one sold under the trade nameMethocel A15LV, and manufactured by Dow Chemicals. Alternatively, thepolymeric coating is polyvinyl alcohol (PVA) having a molecular weight,desirably in a range of from about 5000 to about 100,000, and preferablyfrom about 13,000 to about 23,000. The preferred PVA is from about 87%to about 89% hydrolyzed, such as a commercially available product havinga trade name Airvol 205. Further, the particles are insoluble in theliquid automatic dishwashing detergent composition and only soluble inthe wash solution during automatic dishwashing.

Process for Spraying Colored Polymeric Coating on Particles

The process by which the colored polymeric coating is prepared anddeposited upon the particle is critical in order for the particles toremain undissolved in the liquid automatic dishwashing detergentcomposition and only become soluble in the wash solution duringautomatic dishwashing. It is desirable that the particles dispersed inthe liquid ADW compositions do not break up or dissolve in thecomposition. It is also desirable that this be achieved withoutdepositing an unduly thick coating of a polymeric material on theparticle. It has been surprisingly discovered that when the polymericmaterial, such as methyl cellulose is sufficiently hydrated beforespraying on the particle or prill, the polymer coated particle or prillremains stable, unbroken and undissolved in the liquid ADW composition.This hydration is achieved by forming a sprayable aqueous solution ofthe polymer (alkyl cellulose ether and/or polyvinyl alcohol) having apolymer concentration desirably in a range of from about 1% to about 30%by weight, preferably in a range of about 3% to about 20%, morepreferably in a range of about 3% to about 10%, and most preferably,about 5%. Further, the temperature of aqueous solution of the polymer isdesirably maintained within a range of from about 30° C. to about 40° C.while spraying the polymer solution on the particle, and preferably in arange of from about 32° C. to about 38° C., and most preferably at atemperature of about 35° C. It has been surprisingly found that by usinga combination of the above process steps, i.e., the polymer solutionbeing in a range of from about 1% to 30% by weight, and the spraytemperature being in a range of from about 30° C. to about 40° C., thata very stable, unbroken, continuous coating is formed on the particle orprill which is undissolved in the liquid ADW composition but soluble inthe wash solution, while at the same time, requiring only about 5%polymer by weight of the particle. In the preferred embodiment, thecoating is desirably present in an amount in a range of from about 1% toabout 25% by weight of the particle, preferably from about 4% to about10% by weight of the particle, and most preferably, about 5% by weightof the particle. The reduced coating weight levels are desirable so thatthe least effective coating amount is used in order to accomplish theobjective to having a protective coating without unnecessary polymerthat might detrimentally contribute to unwanted residue deposition inthe washing machine.

Color

In one embodiment, the particles are colored and the automaticdishwashing liquid detergent composition is clear or translucent, so asto make the liquid automatic dishwashing product aesthetically pleasing.In another embodiment, the particles and the liquid automaticdishwashing detergent composition are both colored and the color of theparticles is matched to the base color of the liquid composition. In oneembodiment, the particles have a dark green color whereas the liquidcomposition has a light green color. Other preferred color combinationsfor the polymeric coating on the particles and the liquid automaticdishwashing composition are: blue:blue, blue:white, green:green,green:white and green:yellow, respectively.

Desirably, the particles comprise from about 0.1% to about 5.0% byweight of the liquid composition, and preferably, from about 0.2% toabout 1.0% by weight of the liquid composition.

In another embodiment of the present invention, a non-staining coloredcomposite particle suitable for incorporation in a bleach-containingliquid detergent composition is disclosed. The particle is made by theprocess as set forth above.

Particles

The particles can be formed from various materials that do not cause anydetrimental affect upon the performance of the liquid detergent.Preferably, the particles are in the form of prills. The prillstypically have a core which is coated with a polymeric coating asdescribed before. The core can be made from sucrose, as an example. Themethod of forming prills is well known to those skilled in the art andis disclosed in the literature, such as for example, in U.S. Pat. No.4,965,012, which is incorporated herein by reference.

The particles can be of various sizes and shapes, such as spherical,oval, cylindrical or polygonal and desirably have a particle size in arange of from about 200 μm to about 5000 μm, preferably, from about 400μm to about 2000 μm, and most preferably, from about 500 μm to about 850μm.

In yet another embodiment of the present invention, a liquid automaticdishwashing detergent product is disclosed. The product includes aliquid dishwashing detergent composition containing chlorine bleach, andnon-staining colored composite particles. The particles are made by theprocess as set forth above.

Liquid Automatic Dishwashing Composition Components

The liquid automatic dishwashing detergent product is highly viscous ina quiescent state and has a relatively high yield stress values. Whensubjected to shear stresses, however, such as being shaken in acontainer or squeezed through an orifice, the product quickly fluidizesand upon cessation of the applied shear stress, quickly reverts to ahigh viscosity state. The above liquid automatic dishwashing detergentproduct is preferably low foaming, readily soluble in the washing mediumand most effective at pH values best conducive to improved cleaningperformance, such as in a range of desirably from about pH 7.0 to aboutpH 13.0, and preferably from about pH 8.0 to about pH 12.0.

The physical stability of the liquid product may be improved and thethickness of the liquid product may be altered by the addition of across linking polyacrylate thickener to the liquid detergent product asa thixotropic thickener.

PH Adjusting Components

The pH adjusting components are desirably selected from sodium orpotassium carbonate or sesquicarbonate, sodium or potassium silicate,citric acid, sodium or potassium bicarbonate, sodium or potassiumborate, sodium or potassium hydroxide, and mixtures thereof. NaOH or KOHare the preferred ingredients for increasing the pH to within the aboveranges. Other preferred pH adjusting ingredients are sodium carbonate,potassium carbonate, and mixtures thereof.

Low Foaming Surfactant

Chlorine bleach stable low foaming surfactants are preferred and suchsurfactants are present in a range of from about 0.1% to about 10% byweight of the liquid composition. Such surfactants are generally knownto one skilled in the art and need not be elaborated here, for purposesof brevity. One example of such a surfactant is an anionic surfactantcommercially available under the trade name Dowfax.

Other Ingredients

The liquid automatic dishwashing detergent composition optionally alsocontains from about 0.5% to about 20% of a dispersant polymer selectedfrom the group consisting of polyacrylates and polyacrylate copolymers,and from about 0.1% to about 5% of a chlorine bleach stable foamsuppressant. Such foam suppressants are well known to those skilled inthe art.

To exemplify various embodiments of the present invention, Sample A ofthe liquid automatic dishwashing detergent product composition isformulated using the below named ingredients, as set forth in Example A.

EXAMPLE A

Ingredient (weight % active) A Sodium Tripolyphosphate 17.5 PotassiumTripolyphosphate — Sodium Silicate 6.0 Potassium hydroxide 3.6 Sodiumhydroxide 2.0 Polyacrylate polymer 1.0 Nitric Acid 0.012 Perfume 0.03Nonionic surfactant — Sodium Benzoate 0.75 Sodium hypochlorite 1.15Polyacrylate polymer thickener 1.5 Dye solution — Solid Prill 0.5 WaterBal. TOTAL 100.0

In the above composition, the non-staining colored particles having aspherical shape, and a diameter of about 750 μm, are formed from asucrose core coated with a polymeric coating formed from methylcellulose (Methocel A15LV), and having a bluish-green color. Thebluish-green color is imparted by adding a pigment into the methylcellulose coating before spraying it on the particle according to theprocess of the present invention. The particles comprise about 0.1% toabout 5% by weight of the liquid composition. The optimum methylcellulose coating is about 5% by weight of the particle. The coating issprayed on the sucrose core particle by spraying a 5% by weight aqueoussolution of methyl cellulose with pigment. The aqueous solutiontemperature being carefully maintained at about 35° C. The size of thepigment particles in the aqueous solution is no greater than about 1 μm.The resultant particles are insoluble in the liquid composition but aresoluble in the wash solution during automatic dishwashing. The resultantcolored particles are also non-staining to plastic surfaces.

Accordingly, having thus described the invention in detail, it will beobvious to those skilled in the art that various changes may be madewithout departing from the scope of the invention and the invention isnot to be considered limited to what is described in the specification.

What is claimed is:
 1. A process for forming a non-staining coloredcomposite particle suitable for incorporation in a bleach-containingliquid detergent composition, comprising the steps of: a) forming acolored liquid dispersion of pigment particles in a first liquid medium,wherein the size of said pigment particles in said colored liquiddispersion is no greater than about 5 μm; b) mixing said colored liquiddispersion with a polymeric material and a second liquid medium to forma sprayable colored polymeric material, said polymeric material beingselected from the group consisting of alkyl cellulose ethers andpolyvinyl alcohol; and c) spraying said colored polymeric material on acomposite particle, and forming a colored polymeric coating on saidcomposite particle.
 2. The process according to claim 1, wherein thesize of said pigment particles in said colored liquid dispersion is nogreater than about 1 μm.
 3. The process according to claim 2, whereinthe size of said pigment particles in said colored liquid dispersion isno greater than about 0.1 μm.
 4. The process according to claim 3,wherein the size of said pigment particles in said colored liquiddispersion is no greater than about 0.01 μm.
 5. The process according toclaim 1, wherein the first liquid medium is water.
 6. The processaccording to claim 5, wherein the first liquid medium is water mixedwith up to about 10% by weight of a nonionic surfactant.
 7. The processaccording to claim 1, further including the step of maintaining theamount of surfactants used in said bleach-containing liquid detergentcomposition at a preselected value such that when the bleach-containingliquid detergent composition is diluted in a wash solution, the amountof surfactant delivered in the wash solution is less than criticalmicell concentration.
 8. The process according to claim 1, wherein saidcomposite particle remains insoluble in said bleach-containing liquiddetergent composition but soluble in automatic dishwashing washsolution.
 9. The process according to claim 1, wherein said coloredpolymeric coating is soluble in an automatic dishwashing wash solutionand leaves no significant residue.
 10. The process according to claim 1,wherein said colored polymeric coating is formed from methyl cellulose.11. The process according to claim 10, wherein said colored polymericcoating is formed from methyl cellulose having a molecular weight in arange of from about 5,000 to about 100,000.
 12. The process according toclaim 1, wherein the step of spraying said colored polymeric material ona composite particle includes the step of forming a sprayable aqueoussolution of a polymeric material, said polymeric material being presentin said sprayable aqueous solution in an amount in a range of from about1% to about 20% by weight.
 13. The process according to claim 12,wherein said polymeric material is present in said sprayable aqueoussolution in an amount in a range of from about 3% to about 10% byweight.
 14. The process according to claim 12, wherein the temperatureof said sprayable aqueous solution is maintained within a range of fromabout 30° C. to about 40° C. while spraying.